Another oddity has been the failure of party leaders to lead. As was soon noticed when we released some "top lines" from our New Statesman/ICD poll[5] on Thursday, British National Party voters were "defying" Nick Griffin's leadership and backing AV by 72 to 18 per cent. It was less noticed that Ukip voters were rejecting AV (64 per cent against, 35 per cent for) at exactly the time Farage was appearing on stage with the Yes camp.

Some supporters of the No campaign seized on the former figures as evidence that AV does indeed benefit the BNP. That's not quite the case. Once again they have conflated the party with those inclined to support it.

Another interpretation of the 72 per cent figure is that BNP-inclined voters are making their decision on AV based on self, not party, interest. Griffin is against AV because it gets him no nearer representation at Westminster; BNP supporters are in favour because it allows them to register their protest (however objectionable it is to the rest of us) but still have a say by backing a mainstream party as a second preference.

There's an inherent logic here which explains why the vast majority are unwilling to follow the BNP leadership. It is the same logic that explains why 63 per cent of Greens, too, back AV, albeit in line with their leadership. This is not about left and right.

It is only surprising that Ukip supporters aren't using the same thought process. But perhaps they consider themselves not as a fringe party but as a major force awaiting a breakthrough. In the 2010 general election, Ukip garnered 919,486 votes, giving it by far the biggest share of all the minor parties.

The Scottish National Party provides a penultimate example of leadership and support base at odds. Alex Salmond has agreed to back AV despite some misgivings (he doesn't think it goes far enough and worries that multiple votes on 5 May will take the spotlight off Holyrood elections on the same day), but 53 per cent of likely SNP voters will put a cross in the box marked "No" on Thursday, with only 30 per cent voting Yes to AV.

Which leaves us with the strange case of the Labour Party. Long since split on the merits of Nick Clegg's "miserable little compromise" – and on electoral reform more broadly – Labour is effectively unleadable on the issue. Political expediency may have prompted Gordon Brown to back an AV referendum just before last year's election, but it was hardly a full-throttled endorsement – his deathbed conversion was so close to his own political expiry that the necessary legislation failed to make it on to the statute book in time.

Long-held positions on electoral reform among MPs and the party in the country alike meant that AV was always going to be the ultimate free vote; nothing whippable here. Nevertheless, that Miliband has failed to convince his party's followers to back him – or, at the very least, his inability to move polling numbers incrementally – is a concern. Among those certain to vote, there remains a 5-point advantage for the Noes.

Perhaps he can turn all those undecided Labour supporters – a sizeable 12 per cent of those certain to vote and 18 per cent of all respondents – into pro-AVers between now and Thursday. If he can, he might just cause, six days out, a major upset and reap the political dividend.

More likely, the Labour vote will remain split, marginally favouring the status quo. While his discomfort won't be as a acute as Clegg's, Miliband will nevertheless have questions to answer.

The kind of unholy alliance that paired Cameron with Reid helps explain away some of this, but not all.